PyData Amsterdam 2026

A/B Testing Plenary Debates in the Dutch Parliament with Multi-Agent AI using LangGraph

How do you test systemic democratic reforms when you can’t run live experiments on a
national parliament?

In collaboration with Dutch think-tank DenkWerk for their report “Democracy in Revision”, we
built a multi-agent digital twin of the Dutch House of Representatives. By configuring 15
party agents, a chairperson, and a minister, we simulated parliamentary debates to evaluate
structural reforms, such as introducing electoral thresholds.
In this talk, we break down the engineering and data science setup behind this multi-agent
architecture to simulate a debate. We’ll cover how we translated parliamentary procedure
into a LangGraph state machine, grounded agents using party-filtered RAG, and set up an
experimental framework to A/B test systemic reforms across 238 simulated debates and five
legislative bills.


Simulating real-world human institutions with LLMs introduces unique technical challenges.
For example, how do you enforce strict procedural rules without destroying dynamic debate
flow? How do you keep agents grounded in distinct political identities without leaning into
caricature? And how do you measure the systemic impact of structural changes? These
topics will be addressed in this presentation.

Outline:

  1. Introduction & Problem Statement (4 min): Context on parliament simulation,
    project scope, and the motivation behind modeling democratic reforms.
  2. Architecture & Deterministic State (6 min): Using LangGraph to manage state
    transitions, turn-taking, and procedural parliamentary rules throughout the debate.
  3. Traceability & Debugging (3 min): Using LangSmith to monitor prompt inputs, tool
    calls, and token costs for debugging
  4. Grounding Agents & Mitigating Bias (6 min): Combining structured context,
    party-filtered RAG, and voting histories to ground agent speeches and reduce base
    model bias.
  5. A/B Testing Systemic Reforms & Findings (7 min): Evaluates structural
    democratic reforms by simulating 238 debate runs to measure their impact on debate
    quality and policy outcomes.
  6. Limitations & Conclusions (4 min): Addressing the inherent limitations of using
    LLMs for simulations and validating transcripts with domain experts.
  7. Q&A

Takeaways:

  • How do you transfer a real-world system such as debates into a full multi-agent
    simulation
  • How to control next-turn decisions in this multi-agent using custom bidding phases
  • Grounding the agent personas using RAG to make sure the agent doesn’t rely on
    internal knowledge
  • How to create an A/B experiment to test systemic changes.

Impact

The impact of this project created additional evidence that reforms in the parliament are
necessary. The findings have been used in a report by this think tank with advice on how to
strengthen democracy and is read by politicians, journalists and policy experts.
Generalized applications
This multi-agent simulation could be interesting in any team environment where you would
like to have multiple agents with distinct opinions, expertise and philosophies. You could
instruct them to come to a consensus and see how that plays out. For instance, engineering
teams, executive boards, focus groups or cross-functional teams could be simulated.

Generalized applications

This multi-agent simulation could be interesting in any team environment where you would
like to have multiple agents with distinct opinions, expertise and philosophies. You could
instruct them to come to a consensus and see how that plays out. For instance, engineering
teams, executive boards, focus groups or cross-functional teams could be simulated.

Target audience

This talk is interesting for Machine Learning Engineers, Data Scientists, and Developers who
want to start or have experience with building AI agents, RAG and layered prompting

Jeroen Nelen

Jeroen is a Machine Learning Engineer at KickstartAI, a Dutch non-profit focused on accelerating AI adoption. Holding a Master’s degree in Computer Science focused on LLMs and their explainability, he now builds AI solutions for partners such as KLM and bol. In a recent collaboration with think tank DenkWerk, he developed this simulation as an additional empirical proof point for the latest report, Democracy in Revision.